A Possible Thermodynamic Approach to the Change of Rectal Temperature of Rabbits Due to Forced Restricting Conditions

It was found that the rectal temperature of rabbits restricted by a normal neck stock position dropped about 1.2-1.5°C when the reastriction position chenged from a normal restriction to a supine restriction position. This temperature change was also reversible. We studied the mechanisms of this phenomenon from a thermodynamic point of view and obtained the following results : 1) The rectal temperature of rabbit restricted in the supine position did not increase after the injection of lipopolysaccharide (LPS). 2) In the supine restricted rabbit, endogenous pyrogen which was induced by the injection of LPS to these rabbits appeared the same as the control. 3) Some pharmaceuticals(urethan, iproniazid, atropin and hexamethonium) did not show any influence on the drop of rectal temperature in either normal or supine restrictions. 4) The rectal temperature of shorn rabbits dropped more than that of normal rabbits in both normal and supine restrictions. 5) When the normal restriction position was changed to the supine and prone restriction positions, the mean surface temperature was also decreased. From these results, it was concluded that rabbit rectal temperature was changed with a change in the restriction position which could change the surface skin area.